Gangsters appear if I am so upset (7)
I believe the answer is:
mafiosi
'gangsters' is the definition.
(I have seen 'Sicilian gangsters ' mean 'mafiosi' so perhaps 'gangsters' could also mean 'mafiosi')
'if i am so upset' is the wordplay.
'upset' is an anagram indicator.
'if'+'i'+'am'+'so'='ifiamso'
'ifiamso' anagrammed gives 'MAFIOSI'.
'appear' is the link.
This may not be right. It may be part of another bit of the clue.
Can you help me to learn more?
(Other definitions for mafiosi that I've seen before include "Cosa Nostra members" , "Sicilian gangsters" , "Organized criminals" , "People in Italian criminal organisation" , "Italian gangsters" .)